A dual view field display technology refers to a technology by which different contents can be watched in two view fields on two sides of a display screen. A dual view field device usually comprises one display screen and one barrier, as shown in FIG. 1. A display screen 1 comprises a plurality of pixel units, each of the pixel units includes a sub-pixel electrode 11 for display of one certain view field and a control circuit (such as a TFT circuit) covered by a black matrix 12, and such a pixel structure is generally called as “sub-pixel structure”. The width of the sub-pixel electrode 11 is P, the width of the black matrix 12 between two adjacent sub-pixel electrodes is B, the distance between a barrier 2 and the display screen 1 is H, and the distance from the projection of an edge of an opening of the barrier 2 at the location of the sub-pixel electrode 11 on the display screen 1 to an edge of the black matrix 12 is A. The centerline of the opening of the barrier coincides with the centerline between two adjacent sub-pixel electrodes, so the width of the opening of the barrier is B+2A. An angle θ is the angle of a single view field, and only within this range, a viewer can see light emitted by a sub-pixel as a point. The visible range of the single view field can be enlarged by increasing the angle θ, and in turn, the display quality of the dual view field display device can be improved. Among the angle θ and P, H, A, and B, there is a relationship as represented by the following formula 1:
                              tan          ⁢                                          ⁢          θ                =                  HP                                    H              2                        +                                          (                                  B                  +                  A                                )                            ⁢                              (                                  B                  +                  A                  +                  P                                )                                                                        formula        ⁢                                  ⁢        1            
As can be seen from the formula 1, when the distance A from the projection of the edge of the opening of the barrier at the location of the sub-pixel electrode on the display screen to the edge of the black matrix 12 and the width B of the black matrix between two adjacent sub-pixel electrodes are constant, in order to increase the angle θ, it is necessary to decrease the distance H between the barrier and a light point of the color filter substrate is accordingly, or to properly to reduce the width P of the sub-pixel electrode. As to the prior art, when a Thin Film Transistor Liquid Crystal Display (TFT-LCD) is adopted as the display device, decreasing of the distance H between the barrier and the light point of the color filter substrate means reduction in thickness for a color filter glass. However, it is very difficult to produce an ultrathin color filter glass, and moreover, as the thickness of the color filter glass is decreased, the sturdiness of the color filter glass substrate will also be degraded greatly, which will severely affect the quality of the liquid crystal display device. The structure of a TFT array substrate of an existing dual view field liquid crystal display device is shown in FIG. 2, in which one pixel unit 2 includes a sub-pixel electrode 21 and a TFT circuit 22. In the pixel unit 2, the width P of the sub-pixel electrode 21 is usually 50 μm. When the width P of the sub-pixel electrode 21 is reduced to a very small value (such as 3 μm), it is difficult to decrease the TFT circuit 22 in the same proportion as the width P of the sub-pixel electrode is reduced. The proportion of the black matrix shielding the TFT circuit to the sub-pixel region will be increased accordingly, so that the aperture ratio is reduced significantly and the quality of the liquid crystal display device is affected. When an Organic Light Emitting Diode (OLED) is adopted as the display device, decreasing of the distance H between the barrier and the light point also demands reduction in thickness of a glass substrate.
As can be seen, as to the prior art, in order to enlarge the visible range of each single-side view field for a dual view field display device, it is necessary that the thickness of a glass substrate be decreased, and this leads to rising of production costs and a significant degradation of yield and reliability of substrates.